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Nutrition (Ch. 25)
Nutrition, Metabolism & Body Temperature Regulation
| Question | Answer |
|---|---|
| what is ATP | the chemical energy form used by cells to drive their many activities |
| the energy value of foods is measured in units called | kilocalories |
| one kilocalorie is the | amount of heat energy needed to raise the temperature of 1 kilogram of water 1C & is the unit conscientiously counted by dieters |
| major nutrients are | carbohydrates, lipids & proteins |
| what is a nutrient | a substance in food that is used by the body to promote normal growth, maintenance & repair |
| essential nutrients | cannot be made by such interconversions & must be provided by the diet |
| what is cellulose | a polysaccharide plentiful in most vegetables, not digested by humans but provides roughage or fiber |
| glucose | is a monosaccharide carbohydrate molecule; major body fuel & is readily used to make ATP |
| carbohydrate digestion yields | gructose & galactose (converted to glucose by the liver before they enter the general circulation) |
| when glucose is present in excess of what the body needs for ATP synthesis, it is | converted to glycogen or fat & stored for later use |
| what is the current recommendation of charbohydrates daily | 125 to 175 grams |
| what is the term used to describe highly refined carbohydrates such as candy & soft drinks | empty calories |
| what are the major sources of unsaturated fats | seeds, nuts & most vegetable oils |
| major sources of cholesterol are | egg yolk, meats (organ meats like liver) & milk products |
| the liver cannot synthesize | linoleic acid, a fatty acid component of lecithin |
| an example of an essential fatty acid is | linoleic acid |
| what do fatty deposits in adipose tissue provide? | (1) protective cushion around body organs such as kidneys & eyeballs (2) insulating layer beneath the skin (3) easy-to-store concentrated source of energy fuel |
| prostaglandins | regulatory molecules; plays a role in smooth muscle contraction, control of blood pressure & inflammation |
| how are prostaglandins formed | from linoleic acid via arachidonic acid |
| why is cholesterol important | it is used as a stabilizing component of plasma membranes & is the precursor from which bile salts, steroid hormones & other essential functional molecules are formed |
| daily cholestrol intake should be | no more than 200 mg (the amount of one egg yolk) |
| name two drawbacks to most fat substitutes | (1) don't stand up to the inense heat needed to fry foods (2) dont taste nearly as good as the "real thing"; the ones that are not absorbed tend to cause flatus (gas) & may interfere w. absorptionof fat-soluble drugs & vitamins |
| what are complete proteins | they meet all the body's amino acid requirements for tissue maintenace & growth |
| what is the importance of proteins in the body? | keratin of skin, collagen & elastin of connective tissues & muscle proteins |
| what is the all or none rule | all a.a. needed to bake a particular protein must be present in a cell @ the same time; if one is missing protein will not be made |
| why does this happen | b.c. essential amino acids cannot be stored, therefore those not used immediately to build proteins are oxidized for energy or converted to carbohydrates or fats |
| what happens if the diet does not supply sufficient carbohydrate or fat calories for ATP production | dietary & tissue proteins are used for energy |
| what is the percentage of nitrogen content of protein | 16% |
| when is the body in nitrogen balance | when the amount of nitrogen ingested in proteins equals the amount excreted in urine & feces |
| explain when the body is in positive nitrogen balance | when protein synthesis exceeds protein breakdown & loss (normal in growing children & pregnant women); also occurs when tissues are being rebuilt or repaired following illness or injury |
| what does a positive nitrogen balance always indicate | that the amount of protein being incorporated into tissue is greater than the amount being brokendown & used for energy |
| a negative nitrogen balance is | protein breakdown exceeds the use of protein for building structural or functional molecules |
| when would negative nitrogen balance occur | during physcal & emotional stress (infection, injury, burns, depression or anxiety) during starvation |
| what are anabolic hormones | they accelerate protein synthesis & growth |
| give an example of how an anabolic hormone works | pituitary growth hormone stimulates tissue growth during childhood & conserves protein in adults |
| give another example | the adrenal glucocorticoids released during stress, enhance protein breakdown & conversion of amino acids to glucose |
| most vitamins function as ____ | coenzymes; that is they act w. an enzyme to accomplish a particular chemical task |
| why are vitamins crucial | they help the body to use those nutrients that do; w.o. them all carbs, proteins & fats would be useless |
| where is vitamin D made | in the skin |
| what vitamins are syntehsized by intestinal bacteria | B & K |
| how are vitamins classifyied | as fat soluble or water soluble |
| what are examples of water souble vitamins | B-complex vitamins & vitamin C |
| what are water souble vitamins | they are absorbed along w. water from the gastrointestinal tract (w. exception to B12 which must bind to gastic intrinsic factor to be absorbed) |
| water-souble vitamins can easily be stored & if theyre not used can be | excreted in urine |
| what are the fat-soluble vitamins | A, D, E, K |
| what do fat-soluble vitamins | they bind to ingested lipids & are absorbed along w. their digestion products |
| what can interfer w. fat-soluble vitamins | anything that interferes w. fat absorption |
| what are antioxidants | they disarm tissue-damaging free radicals & have anticancer effects |
| what are examples of antioxidants? | vitamins A, C, & E |
| list the 7 minerals needed | calcium, phosphorus, potassium, sulfur, sodium, chloride & magnesium |
| what is the purpose of calcium, phosphorus & magnesium salts | they harden the teeth & strengthen the skeleton |
| most minerals | are inonized in body fluids or bound to organic compounds to form molecules such as phospholipids, hormones, enzymes & other functional proteins |
| give an example of how this works | iron is essential to the oxygen-binding heme of hemoglobin; sodium & chloride ions are major electrolytes n blood that help maintain (1) normal osmolarity & water balance of body fluids (2) responsiveness of neurons & muscle cells to stimuli |
| anabolism | synthetic; includes reactions in which larger molecules or structures are built from smaller ones; ex. bonding of amino acids to make proteins & of proteins & lipids to form cell membranes |
| catabolism | process that break down complex structures to simpler ones; ex. hydrolysis of foods in the digestive tract |
| cellular respiration | primary function is to generate ATP, which traps some of the chemical energy of the original food molecules in its own high-energy bons; group of reactions which food fuels (particularly glucose) are broken down within cells & some of the energy released |
| phosphorylated | when enzymes shift their high-energy phosphate groups to other molecules |
| what does phosphorylation do | it energizes, or primes, the molecule to change in a way that increases its activity, produces motion or does work; ex. many regulatory enzymes that catalyze key steps inmetabolic pathways are activated by phosphorylation |
| oxidation reactions | the energy-yielding (ATP-yeilding) reactions within cells; |
| when does oxidation occurs | via the gain of oxygen or the loss of hydrogen |
| when on substance loses electrons it is | oxidized |
| when one substance gains electrons it is | reduced |
| redox reactions means that | "oxidized" substances lose energy & "reduced" substances gain energy as energy-rich electrons are transferred from the first to the second |
| dehydrogenase | when enzymes that catalyze oxidation-reduction reactions by removing hydrogen |
| oxidases | those catalyzing the transfer of oxygen |
| coenzymes | act as reversible hydrogen (or electron) acceptors, becoming reduced each time a substrate is oxidized |
| NAD+ | nicotinamide adenine dinucleotide; based on niacin |
| FAD | flavin adenine dinucleotide; derived from riboflavin |
| substrate-level phosphorylation | occurs when high-energy phosphate groups are transferred directly from phosphorylated substrates (metabolic intermediates) to ATP |
| the enzymes catalyzing substrat-level phosphorylation are located in both the | cytoplasm & in the watery environment inside the mitochondria (mitochondrial matrix) |
| oxidative phosphorylation | releases most of the energy that is eventually captured in ATP bonds during cellular respiration |
| how is the oxidative phosphorylation process carried out? | by electron transport proteins forming part of the cristae membranes in the mitochondria |
| chemiosmotic process | couples the movement of substannces across membranes to chemical reations; some of the energy released during the oxidation of food fuels is used to pump hydrogen ios or protos across the inner mitochondrial membrane into the intermembrane space; creating |
| ATP synthase | a membrane channel protei that allows protons to flow back across the membrane |
| the catabolic & anabolic pathways for carbohydrates all begin with | glucose-6-phosphate |
| glycolysis | "sugar spliting"; 10 chemical steps; |
| glycolysis results in | two pyruvic acid molecules; yielding a net gain of 2 ATP per glucose molecule; 2 moecules of reduced NAD+ |
| where does glycolysis occur | in the cytosol of cells, where its steps are catalyzed by specific soluble enzymes |
| what type of process is glycolysis | an anaerobic process; meaning it does not use oxygen & occurs whether or not oxygen is present |
| In step 1 of glycolysis ATP is | consumed-an energy investment that will be repaid with dividends later in glycolysis |
| are the steps in glycolysis reversible | all except the 1st one |
| list the 3 main stages in glycolysis listed in the book | 1. sugar activation 2. sugar cleavage 3. oxidation & ATP formation |
| what's going on during the 2nd stage | fructose-1, 6-diphosphate is split into 3-carbon fragemnts that exist (reversibly) as one of 2 isomers; glyceraldehyde 3-phosphate or dihydroxyacetone phosphate |
| lactic acid is the production yeild of | two adition hydrogen atoms to pyruvic acid |
| when glucose is completely oxidized how many ATP/glucose molecues are harvested | 36 |
| where does the Krebs cycle occur? | in aqueous mitochonrial matrix & is fueled largely by pyruvic acid produced during glycolysis & by fatty acids resultig from fat breakdown |
| what is the first order of bussiness during the Krebs cycle after pyruvic acid enters the mjitochondria | to convert it to acetyl CoA |
| 1) decarboxylation | when one of the pyruvic acid's carbons is removed & released as carbon dioxide gas (a waste product of metabolism) CO2 diffuses out of the cells into the blood to be expelled by the lungs |
| 2)oxidation | the removal of hydrogen atoms; the removed hydrogens are picked up by NAD+ |
| how is acetyl coenzyme A the final product | by combining the resulting acetic acid w. coenzyme A |
| what is coenzyme Al | a sulfur-containing coenzyme derived from pantothenic acid , a B-vitamin |
| keto acids | when atoms of citic acid are rearranged to produce different intermediate molecules |
| what are the products of the Krebs Cycle/Citric acid cycle | 2 molecules of carbon dioxide & 4 molecules of reduced coenzymes (3NADH + H+ & 1 FADH2) |
| electon transport chain | oversees the final catabolic reations that occur on the inner mitochondrial membranes |
| whats going on during the ETC | the hydrogens removed during the oxidation of food fuels are finally combined w. molecular oxygen, & the eergy released during those reactions is harnessed to attach inorganic phosphate groups (Pi) to ADP |
| cofactors | proteins bound to metal atoms |
| where do flavins derive from | the vitamin riboflavin |
| list the sequence energy flows during cellular respiration | glucose-NADH + H+ - electron transport chai - proton motive force - ATP |
| the 8 NADH + H+ & the 2 FADH2 produced during the KRebs cycle are "worth" | 24 & 4 ATPs |
| the 2 NADH + H+ generated during glycolysis yields how many ATP molecules | 4 (or 6) ATP molecules |
| complete oxidation of 1 glucose molecule to carbon dioxide & water yields | 38 or 36 molecules of ATP |
| glycogenesis | occurs when (glycolysis is "turned off" by high ATP levels, glucose molecules are combined in long chains to form glycogen); |
| how does glycogenesis begin | when glucose entering cells is phosphorylated to glucose-6-phosphate & the coverted innto its isomer, glucose-1-phosphate |
| glycogenolysis | occurs when blood levels of glucose drop, glycoge lysis or splitting occurs |
| beta oxidation | the initial phase of fatty acid oxidation, ocurs in the mitochondria |
| glyceraldehyde is equal to | half a glucose molecule & ATP energy harvest from its complete oxidation is approx. 1/2 that of glucose (18 ATP/glycerol) |
| lipogenesis | triglyceride sythesis; occurs when cellular ATP & glucose levels are high |
| lypolysis | (fat-splitting); the breakdown of stored fats into glycerol & fatty acids, essentially lipogenesis in reverse |
| Before amino acids can be oxidized for energy they must be | deaminated; their amine group (NH2) must be removed; resulting molecule then converted to pyruvic acid or one of the keto acid inntermediates in the Krebs cycle |
| what state does the body exist in | dynnamic catabolic-anabolic state |
| what are the differences between the carbohydrate/fat pool & the amino acid pool? | 1) fats & carbohydrates are oxidized directly to produce cellular energy, whereas a.a. can be used to supply energy only after being converted to a carbohydrate intermediate (keto acid) 2) excess carb. & fat can be stored as such, whereas excess aa are no |
| absorptive state | fed state; the time during & shortly after eating, when nutrients are flushing into the bloodstream fm the gastorintestinal tract |
| postabsorptive (fasting) state | period when the GI tract is empty & energy sources are supplied by the breakdown of body reabsorbes |
| elevated amino acid levels in the blood stimulate | insulin release |
| what type of hormone is insulin | a hypoglycemic hormone |
| glucose sparinng | the increased use of noncarbohydrate fuel molecules (especially triacylglycerols) to conserve glucose |
| glucagon | insulin antagonist |
| what type of hormone is glucagon | hyperglycemic hormone; promotes a rise in blood glucose; targets the liver & adipose tissue |
| increasing blood sugar levels trigger | insulin release |
| which "pushes"___ into the cells | glucose |
| blood sugar levels | decline |
| when blood sugar levels are low the secrtion of ___ occurs | glucagon |
| which ___ | pulls glucose from the cells into the blood |
| growth hormonne secretion is enhanced by | prolonnged fasting or rapid declines in plasma glucose levles, & it exerts important ant-insulin effects |
| list the functions of the liver | 1) packages fatty acids into forms that ca be stored or transported 2) synthesizes plasma proteins 3) forms nonessential aa & convertes ammonia resulting from their deamination to urea a less toxic excretory product 4)stores glucose as glycogen & regulate |
| cholesterol | dietary lipid; serves as the structural basis of bile salts, steroid hormones & vitamin D & a mj component to plasma membrane |
| chylomicrons | transport absorbed lipids from the gastrointestinal tract, considered as a separate class & have the lowest density of all |
| what is the role of LDLs | to transport cholesterol tot he peripheral tissues, makinng it available tot he tissue cells for membrane or hormone synthesis & for storage for later use; also regulate cholesterol synthesis in the tissue cells |
| what is the function of HDLs | to transport excess cholesterol from peripheral tissues (which do not have the ability to degrade or excrete HDL) to the liver, where it is broken down & becomes part of bile |
| HDL is considered | good |
| LDL is considered | BAD TO THE BONE!!! |
| what is wrong with LDL | it promotes plaque formation that thickens & stiffens the blood vessel walls |
| saturated fatty acids stimulate ____ of cholesterola & _____ from the body | liver synthesis; inhibit its excretion |
| what is energy intake | total energy output (heat + work + energy storage) |
| EI | is considered equal tot eh energy liberated during food oxiation; undigested foods are not part of the equation bc they contribute to no energy |
| Energy output | includes the energy (1) immediately lost as heat (about 60% of the total); used to do work ; stored in the form of fat or glycogen |
| orexins | a pair of peptides that are powerful appetite enhances |
| neuropeptide Y causes | us to crave carbohydrates |
| galanin | produces a yen for fats |
| GLP-1 & serotonin | (glucagon-like peptide); make us feel full & satisfied |
| when we eat plasma glucose levels ___ & cellular metabolism of glucose __ | increases; increases |
| elevated plasma levels of amino acids ___ eating; wheras low amino acid levels in blood ___ it. | depress eating; stimulate it |
| insulin released during food absorption has what effect on hunger | depresses hunger |
| glucagon levels rise during what type of behavior | fasting; stimulate hunger |
| when is epinephrine release & what does it trigger | (released during fasting); triggers hunger |
| what is cholecystokinin & what effect does it have on hunger? | a hormone released in the intestines; it is secreted during food digestion which depresses hunger |
| increased body temperature may have what effect on hunger | it may inhibit it |
| leptin | the overall satiety signal; secreted over a period of hours exclusively by fat tissue in response to an increase in fatty mass in the body; regulated by glucocorticoids & insulin |
| what does leptin bind to | receptors in the choroid plexuses of the ventricles, where it gains entry to the brain |
| leptin acts on the | hypothalamus |
| what does it regulate | the amount of body fat via controls of appetite & energy output |
| what is leptins main target of action | the ventromedial hypothalamus, where it suppresses the secretion of nneuropeptide Y (NPY); the most potent appetite stimulant known |
| therefore with all that said & done leptin pretty much | decreases food intake & cranks up activity & heat production |
| metabolic rate | the body's rate of eergy output (usually per hour) |
| calorimeter | direct method |
| respirometer | indirect method; measure oxygen consumption, which is directly proportional to heat production |
| BMR(basal metabolic rate) | the measurement obtained; reflects the energy the body nees to perform only its most essential activities |
| the taller or thinner person will have a ___ BMR than a shorter fatter person | higher |
| thyroxine | produced by thyroid gland; important in determing BMR; metabolic hormone |
| TMR (total metabolic rate) | a total rate of kilocalorie connsumption to fuel all ongoing-activities--involuntary & voluntary |
| dietary/food-induced thermogenesis | when food ingestion induces a rapid increase in TMR; is greates when proteins are eatten |
| radiation | loss of heat in the form of infrared waves (thermal energy); close to 1/2 of body heat loss occurs by radiation |
| conduction | transfer of heat between objects that are in direct contact w. each other; ex. when we step into a hot tup, some of the heat of the water is transferred to our skin; conduction requires molecule-to-molecule contact of objectes; thermal energy must move th |
| convection | substantially enhances heat exchange from teh body surface tot eh air bc the cooler air absorbs heat by conduction more rapidly than the already-warmed air |
| the hypothalamus receives afferent input from | peripheral thermoreceptors & central thermoreceptors |
| the hypothalmus respons the heat promoting or heat loss activites via | autonomic effector pathways |
| vasoconstriction of cuanneous blood vessels | blood is restricted to deep body areas & largely bypasses the skin; heat loss from the shell is dramatically reduced & shell temp drops toard that of the external environment |
| increase in metabolic rate | (blank) |
| cold stimulates the relae of | norepinephrine; elevates the metabolic rate; which enhances heat production (known as chemical; nonshivering thermogenesis) |
| shivering | increases body temp bc muscle activity produces large amounts of heat |
| enhanced thyroxine release | occurs when envir temp decreases gradually; hypothalamus releases thyrotropin-releasing hormonne; increases metabolic rate body heat production increases allowing us to maintain a constannt body tempin cold envir condtions |
| vasodilation of cutaneous blood vessels | allows vessels to dialate; skin swell w warm blood, heat is lost from the shell by radiation, conduction & convection |
| enhanced sweatinng | occurs when body is overheated & heat cannot be lost by other means; evaporation |
| fever is controlled | hyperthermia; results from infection; occurs when wbc & macrophages release PYROGENS (fire starters) |
Created by:
Brina
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